This invention relates generally to a transcutaneous electrode design, and more particularly to a novel transcutaneous electrode construction which facilitates the retention of the electrolytic gel and is useful in application of electrical stimulus to nerve tissue, as for example, might be utilized in pain therapy.
In recent years, utilization of electrical nerve stimulus in pain therapy has become increasingly wide spread and accepted as a therapeutic practice. In theory, the applied electrical stimulus results in an "overload" condition of the associated nerve tissues and structures so that a pain stimulus existing on these nerve tissues or structures cannot be transmitted to the brain to produce the normal pain response in the patient. In this regard, the physician or therapist will utilize suitable electrodes connected with a source of electrical current to effect the desired nerve stimulation. However, it will be appreciated that the construction as well as the appearance of conventional metallic electrodes and the like may cause undue alarm to the patient, as well as being relatively inconvenient to handle by the physician or therapist.
The apparatus and procedure utilized generally in pain therapy require that the electrode or electrodes be affixed to the patient's skin adjacent the nerves to be stimulated by use of an adhesive or the like. Also, of importance is the fact that a substantial quantity of electrolytic gel or past material must be employed to assure proper conductive contact with the patient's skin. While prior electrode designs have been used in this type of treatment, they have not proven satisfactory. More specifically, the prior art electrode constructions were developed primarily for the monitoring of bio-medical functions, i.e. ECG's, or for use in electro-surgery, typical examples of which are shown in U.S. Pat. Nos. 3,989,035 and 3,805,796. These prior electrode designs proved unsatisfactory in that they were not able to store or accommodate the necessary or desired quantity of electrolytic gel required for pain therapy use. While these designs employed gel pads formed of a sponge-like material, the quantity of gel that could be stored was limited to that which could be absorbed by the gel pad. If a larger quantity was used, a major portion of the gel was disposed on the exterior of the pad and problems arose upon application of the electrode. In this regard, as the electrode was applied the gel would tend to be squeezed or flow along the interface of the base with the patient's skin, thus preventing proper attachment of the electrode. As will become clear from the discussion to follow, the present invention provides an improved design which is able to accommodate the larger gel quantities needed with transcutaneous electrodes.
In addition to the above-mentioned prior art electrodes, designs have been proposed, which utilize a formed plastic base section that provides a recess for the gel; see U.S. Pat. Nos. 3,862,633; 3,945,384; and 3,865,099. These designs, however, require the molding or vacuum forming of the base section, and are thus expensive to fabricate and assemble.
With the above in mind, it should be noted that the present invention employs a design wherein the electrode is fabricated primarily from sheet material and as such can be manufactured using automated machinery. The advantage of economy of construction and automated manufacture are achieved without relinquishing the advantages of a gel chamber, and this is attained by providing that the gel pad is adhered to the adhesive on the base layer only at is edges. As such, the major portion of the gel pad, which overlied the nonconductive layer, is not affixed to the underlying structure. Accordingly, the gel pad and nonconductive layer serve to define a chamber or pocket, into which a large quantity of gel may be injected and stored. Upon use of the electrode, while the gel can pass through the porous gel pad, and will thoroughly soak the pad, the electrode can be adhered to the patient's skin without the squeezing or migration of gel along the skin interface. Thus, the electrolytic gel is maintained in the area of the gel pad, and is preferred for the efficient and proper operation of the electrode.
Other objects, features and advantages of the present invention will become more readily apparent from the following detailed description of the illustrated embodiment which is presented in conjuction with the accompanying drawings.